Explaining Measurement Distortions: Tiny Border Effects

As physics experiments focus on the atomic scale and smaller, measuring devices become more susceptible to error from physical defects.

In many experiments, measurements are taken by passing particles through an escape hole or open channel. Any physical irregularities in an exit point’s shape, or any shift in the angle from which the particle enters, can misrepresent the device’s signal.

These images are plots tracking subtle signal, or measurement, shifts. The blue image (Figure 1) plots variations in escape time. Changes in aperture shape or moving the incoming angle affect the length of time it takes for a particle to pass through the hole. The lighter lines at the top correspond to longer escape times.

The orange image (Figure 2) illustrates how rounding the entrance hole and shifting incoming angles affect a particle's outgoing angles. In Figure 2, the yellow lines are the result of widening angles while red lines show particle positions when angles were smaller.

Figure 1
measuring variances in escape time
Image Credit: ©2012 American Physical Society
Figure 2
measuring how roundedness affects incoming and outgoing particle angles
Image Credit: ©2012 American Physical Society 

Gray arrow  "Intrinsic stickiness and chaos in open integrable billiards: Tiny border effects," Physical Review E 83, 056201 (2011)

M. S. Custódio and M. W. Beims,
Departamento de Física,
Universidade Federal do Paraná
CEP 81531-990
Curitiba, PR, Brazil

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